Rinse and debeard the mussels. Discard any mussels with broken shells or that remain open after being "tapped".
Heat olive oil in a pressure cooker. Add garlic. Sauté for 2-3 minutes--- just enough to soften the garlic.
Add pesto and capers. Sauté for another 1-2 minutes.
Add tomatoes, broth, fresh herbs, salt and pepper.
Add the mussels, cover and lock pressure cooker lid. Use Seafood setting on electric cooker or cook at full pressure for 2 minutes. Release pressure and open according to the manufacturer's directions for the pressure cooker you are using.
Discard any mussels that have not opened.
Serve soup style.
This recipe is a great starting point to add your own flavors. Shrimp or fish would be an excellent addition.